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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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978b63f746
For fiemap we recently stopped locking the target extent range for the whole duration of the fiemap call, in order to avoid a deadlock in a scenario where the fiemap buffer happens to be a memory mapped range of the same file. This use case is very unlikely to be useful in practice but it may be triggered by fuzz testing (syzbot, etc). This however introduced a race that makes us miss delalloc ranges for file regions that are currently holes, so the caller of fiemap will not be aware that there's data for some file regions. This can be quite serious for some use cases - for example in coreutils versions before 9.0, the cp program used fiemap to detect holes and data in the source file, copying only regions with data (extents or delalloc) from the source file to the destination file in order to preserve holes (see the documentation for its --sparse command line option). This means that if cp was used with a source file that had delalloc in a hole, the destination file could end up without that data, which is effectively a data loss issue, if it happened to hit the race described below. The race happens like this: 1) Fiemap is called, without the FIEMAP_FLAG_SYNC flag, for a file that has delalloc in the file range [64M, 65M[, which is currently a hole; 2) Fiemap locks the inode in shared mode, then starts iterating the inode's subvolume tree searching for file extent items, without having the whole fiemap target range locked in the inode's io tree - the change introduced recently by commit |
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| attr.c | ||
| backing-file.c | ||
| bad_inode.c | ||
| binfmt_elf.c | ||
| binfmt_elf_fdpic.c | ||
| binfmt_elf_test.c | ||
| binfmt_flat.c | ||
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| buffer.c | ||
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| file.c | ||
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| fs_context.c | ||
| fs_parser.c | ||
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| fs_struct.c | ||
| fs_types.c | ||
| fsopen.c | ||
| init.c | ||
| inode.c | ||
| internal.h | ||
| ioctl.c | ||
| Kconfig | ||
| Kconfig.binfmt | ||
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| libfs.c | ||
| locks.c | ||
| Makefile | ||
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| mount.h | ||
| mpage.c | ||
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| namespace.c | ||
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| posix_acl.c | ||
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| readdir.c | ||
| remap_range.c | ||
| select.c | ||
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